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Transcript of PWM square wave inverter
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Report On
PWM Square Wave Inverter Using IRF830B MOSFET (Course: Power Electronics)
Submitted by Submitted to
Sheshadri Shekhar Rauth Shri. Suriya Prakash J
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Contents
SL. N. Contents Page No. 1 Introduction 3
2 Basic Fundamentals 4
3 PWM technologies 7
4 MOSFET Switch 8
5 Components Need for Hardware Implementation 9
6 ARDUINO Program 10
7 Proposed Circuit Diagram and description 11
8 Simulated Circuit & Scope Output 12
9 Analysis & Result 13
10 References 14
SQUARE WAVE INVERTER
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CHAPTER 1
INTRODUCTION
A power inverter, or inverter, is an electronic device or circuitry that changes direct
current (DC) to alternating current (AC).
The input voltage, output voltage, frequency, and overall power handling capacity are
depends on the design of the specific device or
circuitry. The inverter does not produce any power
as the converted power is provided by the DC
source.
A power inverter can be entirely electronic or may
be a combination of mechanical effects (such as a
rotary apparatus) and electronic circuitry. Static
inverters do not use moving parts in the conversion
process.
There are 3 major types of inverters - sine wave
(sometimes referred to as a "true" or "pure" sine wave), modified sine wave (actually a
modified square wave), and square wave.
Inverters can also be used with transformers to
change a certain DC input voltage into a
completely different AC output voltage (either
higher or lower) but the output power must
always be less than the input power: it follows
from the conservation of energy that an inverter and transformer can't give out more
power.
AIM: TO CONVERT DC TO AC
Figure I: An 140W Inverter Image
Figure II: Electrical Sign of an Inverter
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CHAPTER 2
BASIC FUNDAMENTALS
Input voltage
A typical power inverter device or circuit requires a relatively stable DC power source capable
of supplying enough current for the intended power demands of the system. The input voltage
depends on the design and purpose of the inverter. Examples include:
12 VDC, for smaller consumer and commercial inverters that typically run from a
rechargeable 12 V lead acid battery.
24 and 48 VDC, which are common standards for home energy systems.
200 to 400 VDC, when power is from photovoltaic solar panels.
300 to 450 VDC, when power is from electric vehicle battery packs in vehicle-to-grid
systems.
Hundreds of thousands of volts, where the inverter is part of a high voltage direct
current power transmission system.
Output waveform
An inverter can produce a square wave, modified sine wave, pulsed sine wave, pulse width
modulated wave (PWM) or sine wave depending on circuit design. The two dominant
commercialized waveform types of inverters as of 2007 are modified sine wave and sine wave.
There are two basic designs for producing household plug-in voltage from a lower-voltage DC
source, the first of which uses a switching boost converter to produce a higher-voltage DC and
then converts to AC. The second method converts DC to AC at battery level and uses a line-
frequency transformer to create the output voltage.
Square wave
This is one of the simplest waveforms an inverter design can produce and
is best suited to low-sensitivity applications such as lighting and heating.
Square wave output can produce "humming" when connected to audio
equipment and is generally unsuitable for sensitive electronics.
Sine wave
A power inverter device which produces a multiple step sinusoidal AC
waveform is referred to as a sine wave inverter. To more clearly distinguish
the inverters with outputs of much less distortion than the "modified sine
wave" (three step) inverter designs, the manufacturers often use the
Figure III: Square Wave
Figure IV: Sine Wave
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phrase pure sine wave inverter. Almost all consumer grade inverters that are sold as a "pure sine
wave inverter" do not produce a smooth sine wave output at all, just a less choppy output than
the square wave (one step) and modified sine wave (three step) inverters. In this sense, the
phrases "Pure sine wave" or "sine wave inverter" are misleading to the consumer. However, this
is not critical for most electronics as they deal with the output quite well.
Where in power inverter devices for standard line power, a sine wave output is desirable
because many electrical products are engineered to work best with a sine wave AC power
source. The standard electric utility power attempts to provide a power source that is a good
approximation of a sine wave.
Sine wave inverters with more than three steps in the wave output are more complex and have
significantly higher cost than a modified sine wave, with only three steps, or square wave (one
step) types of the same power handling. Switch-mode power supply (SMPS) devices, such as
personal computers or DVD players, function on quality modified sine wave power. AC motors
directly operated on non-sinusoidal power may produce extra heat, may have different speed-
torque characteristics, or may produce more audible noise than when running on sinusoidal
power.
Modified sine wave
A "modified sine wave" inverter has a non-square waveform that is a useful rough
approximation of a sine wave for power translation purposes.
Most inexpensive consumer power inverters produce a modified sine wave rather than a pure
sine wave.
The waveform in commercially available modified-sine-wave inverters is a square wave with a
pause before the polarity reversal, which only needs to cycle back and forth through a three-
position switch that outputs forward, off, and reverse output at the pre-determined frequency.
Switching states are developed for positive, negative and zero voltages.. The peak voltage
to RMS voltage ratio does not maintain the same relationship as for a sine wave. The DC bus
voltage may be actively regulated, or the "on" and "off" times can be modified to maintain the
same RMS value output up to the DC bus voltage to compensate for DC bus voltage variations.
Output frequency
The AC output frequency of a power inverter device is usually the same as standard power line
frequency, 50 or 60 hertz
If the output of the device or circuit is to be further conditioned (for example stepped up) then
the frequency may be much higher for good transformer efficiency.
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Output voltage
The AC output voltage of a power inverter is often regulated to be the same as the grid line
voltage, typically 120 or 240 VAC, even when there are changes in the load that the inverter is
driving. This allows the inverter to power numerous devices designed for standard line power.
Some inverters also allow selectable or continuously variable output voltages.
Output power
A power inverter will often have an overall power rating expressed in watts or kilowatts. This
describes the power that will be available to the device the inverter is driving and, indirectly,
the power that will be needed from the DC source. Smaller popular consumer and commercial
devices designed to mimic line power typically range from 150 to 3000 watts.
Not all inverter applications are solely or primarily concerned with power delivery; in some
cases the frequency and or waveform properties are used by the follow-on circuit or device.
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CHAPTER 3
PULSE WIDTH MODULATION
Pulse-width modulation (PWM), or pulse-
duration modulation (PDM), is
a modulation technique used to encode
a message into a pulsing signal. Although this
modulation technique can be used to encode
information for transmission, its main use is to
allow the control of the power supplied to
electrical devices, especially to inertial loads
such as motors. In addition, PWM is one of the
two principal algorithms used
in photovoltaic solar battery chargers, the other
being maximum power point tracking.
The average value of voltage (and current) fed
to the load is controlled by turning the switch
between supply and load on and off at a fast rate.
The longer the switch is on compared to the off periods, the higher the total power supplied to
the load.The PWM switching frequency has to be much higher than what would affect the load
(the device that uses the power), which is to say that the resultant waveform perceived by the
load must be as smooth as possible. Typically switching has to be done several times a minute
in an electric stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to tens of kHz for a
motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power
supplies.
The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of
time; a low duty cycle corresponds to low power, because the power is off for most of the time.
Duty cycle is expressed in percent, 100% being fully on.
The main advantage of PWM is that power loss in the switching devices is very low. When a
switch is off there is practically no current, and when it is on and power is being transferred to
the load, there is almost no voltage drop across the switch. Power loss, being the product of
voltage and current, is thus in both cases close to zero. PWM also works well with digital
controls, which, because of their on/off nature, can easily set the needed duty cycle.
PWM has also been used in certain communication systems where its duty cycle has been used
to convey information over a communications channel.
Figure V: PWM pulse example
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CHAPTER 4
MOSFET AS A SWITCH
1. Cut-off Region
Here the operating conditions of the transistor are zero input gate voltage ( VIN ), zero
drain current ID and output voltage VDS = VDD. Therefore for an enhancement type
MOSFET the conductive channel is closed and the device is switched “OFF”.
Then we can define the cut-off region or “OFF mode” when using an e-MOSFET as a
switch as being, gate voltage, VGS < VTH and ID = 0. For a P-channel enhancement
MOSFET, the Gate potential must be more positive with respect to the Source.
2. Saturation Region
In the saturation or linear region, the transistor will be biased so that the maximum amount of
gate voltage is applied to the device which results in the channel resistance RDS(on being as small
as possible with maximum drain current flowing through the MOSFET switch. Therefore for the
enhancement type MOSFET the conductive channel is open and the device is switched “ON”.
Figure VI: MOSFET as OFF switch
Figure VII: MOSFET as ON switch
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CHAPTER 5
COMPONENTS NEEDED FOR HARDWARE IMPLEMENTATION
Table I. Components Needed
SL.N. NAME SPECIFICATIONS PICS.
1 ARDUINO UNO R3 with ATmega328 1
2 PC TO PROGRAM ONCE Any programmable PC 1
3 IRF830 VDS = 500V, ID = 5.3A 4
4 TC4427 0.4V to 18V, 1.5A 1
5 RESDISTOR 10K 2
6 CAPACITOR 0.1F 1
7 TRANSFORMER 12V/230V 1
8 BATTERY 12V, 7.5Ah 1
9 DC BULB AS LOAD 9W, 240V, AC 1
10 MULTYMETER --- 2
11 COMMON PCB BOARD 6cm*4cm 1
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CHAPTER 6
USED ARDUINO PROGRAM
The ARDUINO UNO is a microcontroller board based on the ATmega328 (datasheet).
It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog
inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header,
and a reset button.
The program used here to generate PWM signals (complement to each other):
Frequency = 50Hz, Duty Cycle = 50%, Time Period = 0.02 Second, Pulse Width = 0.01
Second
Code:
void setup() {
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}
void loop() {
digitalWrite(9, HIGH);
delay(10);
digitalWrite(9, LOW);
delay(0);
digitalWrite(10, HIGH);
delay(10);
digitalWrite(10, LOW);
delay(0);
}
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CHAPTER 7
PROPOSED CIRCUIT DIAGRAM
Description:
The circuit contains ARDUINO, IRF830 MOSFETs, TC4427, Transformer, Load for
testing, Battery, Resistors, Capacitor, PC for programming, Multi-meter etc. With
ARDUINO software installed PC I have programmed our ARDUINO microcontroller.
Now it can generate two PWM pulses. One is complementary to another. To amplify
these PWM pulses I have used TC4427 as shown above. Those two pulses I have used to
ON & OFF the MOSFET switches simultaneously. The main intention of that MOSFET
maid H-Bridge circuit is to apply positive and negative voltage across the load
periodically, hence producing a pulsating current through it. And the DC source I have
taken from a battery. Now to increase the voltage across the load I have used a
transformer. After completing the total configuration I can check it.
Figure VIII: Basic Square Wave Inverter Circuit
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CHAPTER 8
MATLAB SIMULADET CIRCUIT & THE SCOPE OUTPUT
Figure IX: Basic Square Wave Inverter Simulated Circuit
Figure X: Scope Displayed Wave Forms
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CHAPTER 9
RESULT & ANALYSIS
Result and Analysis:
From that above simulation (Figure IX) I got that above scope output display (Figure X).
From that I have realized the result as bellow.
The input is a 12V, 7.5 Ah Lead Acid battery (DC source)
Output is a 9W 240V AC bulb (AC load)
After running the simulation file on MATLAB I got
Load current Irms =0.04A
Load Voltage Vrms=240V
Output frequency = 50Hz
Power consumed by the load=Vrms*Irms*COS (Ø) = 240*0.04*0.95=9.12W (Taking load
efficiency = 95%)
Current drawn from the battery IB-PEAK=0.8A
Battery voltage=12V
Input Power (DC) = V*I=12*0.8=9.6W
Output power (AC) = 9.12W
System efficiency = (PAC/PDC) = (9.12/9.6)*100 % =95 %
Conclusion:
By simulating this inverter I have got 95% efficiency considering the load power factor =
0.95. If the load had the power factor value 1, than theoretically the simulated inverter
efficiency would be 100%. Though here I have simulated a simple square wave inverter,
the good voltage profile point of view, the output wave form should be as closer as
possible to the sin wave. And that can be done by controlling the switching frequency
and pulse width by a well programmed pulse generator.
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References:
[I] https://en.wikipedia.org/wiki/Power_inverter
[II] https://www.arduino.cc/en/Tutorial/PWM
[III] http://www.electronics-tutorials.ws/transistor/tran_7.html